# Questions tagged [qpsk]

Quadrature Phase Shift Keying

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### MATLAB: Generating a random bit stream in a frequency Band for PSK Modulation

I want to generate a pseudo-random bit stream in MATLAB in a given frequency band for PSK Modulation. I am using the idinput function to generate the bit stream: <...
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### Loop Bandwidth for Carrier Demodulation loop

I am trying to implement a simple MATLAB model for the demodulators for phase modulated signals (PSK) used in communication systems. For the detection of the phase modulated output (PM out in the ...
87 views

### QPSK demodulation problem due to apparent transmitter clock frequency drift

I am using FPGA to generate 10Mbaud QPSK signal in two channels corresponding to two quadratures. Upsampling to 1GSample/s (using raised cos filter for interpolation) and complex upconversion (f_up=...
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### Modulation classification via demodulation confidence?

I'm not sure if this is the right place to post this question, but will try anyway :-) I recently started reading up on the field of automated modulation classification (AMC) where an algorithm ...
141 views

### ADC sampling rate implications Matlab/Simulink M-PSK modulation

I am trying to find a way to evaluate what would be the minimum sampling rate used in a modulated waveform using matlab / Simulink. The real scenario would be let say a M-PSK waveform of Y bandwidth ...
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### Digital Tanlock carrier recovery loop

I’m currently trying to understand a digital tanlock carrier recovery loop for QPSK (for example) I cannot understand how it works. For example we an ideal QPSK constellation. phi = atan2(Q/I) = pi/...
90 views

### Nyquist sampling theorem / Nyquist - Shannon theorem evaluation over M-PSK

I am trying to simulate an M-PSK Tx-Rx System on Simulink and analyse what the effect of sampling rate reduction would have on it. More, particular I am trying to prove what Nyquist sampling theorem ...
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### Learning PSK Modulation and Demodulation - Good Text to Read?

Title sums it up. I am curious to see what you all suggest. I'm a newbie and just need some beginner/intermediate material. Thanks!
355 views

### GNU Radio - Bandwidth and Band Reject Filter

I am currently trying to generate a psk modulated carrier with gnu radio. Attach is an image of my flow graph. As can be seen I am generating a bit stream using the Random Source module and ...
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### BER performance of a space-time code over Rayleigh channel model

For a given space-time code, and in general terms, how would one proceed in the evaluation of the BER performance of this code ? In order to be more clear, say i have 16 code matrices(who's elements ...
604 views

### BER of QPSK modulation in Rayleigh fading channel model

i am having trouble deriving a BER analytical expression for QPSK modulation system operating in a Rayleigh Fading channel model. Could anyone direct me to a reference that would help in this matter. ...
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### How to compare two 802.15.4 O-QPSK modulated digitals signals?

I am working on wireless sensors project and I am trying to simulate a transmission between two nodes. So let's say I have two nodes which transmit the message to each other, i.e. node 1 transmits ...
1k views

### Offset QPSK detection in GNU Radio - Sample delay

An OQPSK detector is being tested in GNU Radio. The architecture was obtained from Michael Rice's Digital Communications - A discrete-time approach. The flowgraph is shown below. The modulator ...
4k views

### Why is bit error rate = symbol error rate / number of bits per symbol in QPSK

I saw a code computing the error probability of QPSK, and I found that in this code the bit error rate is computed as symbol error rate divided by $2$. I think that $2$ is because the QPSK symbol ...
369 views

### “Revolving” QPSK Constellation

I am trying to code a QPSK transmitter in VHDL but first I want to create one out of Simulink blocks and translate it into VHDL code. I am using an example project for the PlutoSDR as a guide. This ...
305 views

### OQPSK vs QPSK envelope query

We use OQPSK because of envelope of signal but my question is "In Phase Shift Keying(or QPSK) the amplitude of the transmitted signal is constant then how the envelope will change in OQPSK"??
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### QPSK Data Rate vs Bandwidth at Passband: Why can it only transmit 1 bit per Hz and not 2 bits per Hz?

1) This is a follow up question to the most up-voted answer to this question. 2) The accepted answer is that "QPSK transmits 1 bit per Hz at passband". 3) The theory found in books seems to agree ...
995 views

### Processing OBPSK as OQPSK

I'm trying to create and process an OBPSK signal, which, as I understand it, transmits even bits on one axis and the odd bits on the opposite axis, resulting in a constellation with 4 unique points. ...
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### QPSK and OQPSK Modulation

In QPSK, after splitting the odd and even bits into the I and Q channels, and then multiplying them with the sine and cosine function, what next am I suppose to do? Do I rearrange them back into ...
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### what waveform using to send qpsk signal with IQ tranceiver

I have an SDR tranceiver (AD9361 on fmcomms3) working with IQ channels, i wanted to make a c++ software that modulate and send a digital QPSK signal but i'm a beginner in digital signal processing and ...
305 views

### SOQPSK-TG pulse shaping

I'm trying to build an SOQPSK-TG signal in MATLAB/Octave. I am following this paper for formulas. I'm trying to generate a waveform for the phase, equation 2.4: Where q(t) is the phase pulse, ...
178 views

### mpsk demodulation using digital sample

I am trying to receive and demodulate a 8PSK modulated sinusoidal waveform (real not complex) which is constant envelop and changing only in phase of the continuous sinusoid carrier every Symbol ...
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### Understanding the over sampling factor effects before a Matched Filter?

I am trying to design a matched filter at the receiver side to a half sine pulse shaping function sent by the transmitter of an OQPSK transceiver. I am not sure I understand the effect of varying the ...
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### QPSK constellation from baseband signal

My IQ sampler is measuring a QPSK carrier at a set frequency/bandwidth (40MSamp/s), but shifts the signal spectrum to baseband. My signal is 1.5Msym/s, but sampling at 1.5Msym/s gives me a ...
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### Phase versus time graph of QPSK

In wikipedia, there was an example on QPSK modulation where the main signal was 11000110 and I contained 1001 and Q contained <...
3k views

### What is a constant envelope modulation?

The Book "Digital Modulation Techniques" by Fuqin Xiong groups digital modulation schemes into two classes: "constant envelope" and "nonconstant envelope." However, I was surprised by the inclusion ...
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### What techniques are available for correcting constellation rotation due to phase ambiguity?

In order for a receiver to recover a baseband signal, it needs a carrier signal equivalent to that used by the transmitter for upconverting the original baseband signal. Unless pilot tones are used, a ...
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### The code explanation about QPSK modulation

This is the code about the QPSK modulation, and I don't understand the real part and the imaginary part code. Can anyone explain it to me if you know? Why is ...
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### Question on the definition of one-sided PSD in AWGN channel

I am currently simulating the following in a telecommunications exercise in Python: Consider a binary sequence $m[n]$ that is being modulated with QPSK (Gray-mapped) that is being transmitted via ...
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### Scatter Plot of OQPSK

Below is my MATLAB code for OQPSK communication: ...
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### Recovering signal for psk

I am currently working on a product(cant disclose too much details of the actual project) in which some data is being sent via audible(but on the higher freq) sound that is encoded with dqpsk. ...
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### QPSK fundamental

I am trying to understand the QPSK fundamental and when I read that the phase shifts are 45°, 135°, 225°, and 315° in QPSK, I can not figure it out how. In other word, I do not understand how the ...
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### QPSK on baseband question

Given a signal you are asked to perform baseband QPSK (not on a carrier). Does this mean the following? In baseband QPSK the (possible) constellation points are \sqrt {E_s} e^{jn \pi / 2} \...
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### What is the theoretical bit error rate for QPSK Matlab simulation when constellation points are transmitted (no symbol duration)?

I'm simulating a QPSK system in Matlab and I'm trying to calculate the theoretical bit error rate to compare it with the simulated ber. The formula that I'm aware of involves the term Eb/N0, but how ...
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### How can I generate offset QPSK symbols from QPSK symbols

I am trying to generate Offset-QPSK modulated symbols. But I am facing some difficulties. I know how to make QPSK symbols but I am unable to figure out at what stage I have to bring in changes to make ...
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### Gardner Timing Recovery for Repeated Symbols

I am implementing the Gardner Timing Error Detection algorithm for a QPSK signal. I understand the concepts behind it but I am curious as to what effect repeated signals can have on the phase lock. ...
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### Noise variance calculation for 16APSK Demodulator

I need to use approximate LLR algorithm for 16APSK demodulation. For that, I need to calculate noise variance which is given as \$Noise\;variance = \frac {Signal\;power\;\times\;Symbol\;time}{Sample\;...
1k views

### Calculating bit-error-rate of QPSK data

I am working on a simulation of QPSK data using the code below (Matlab): ...
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### Creating an Eye Diagram for QPSK Simulation

I am trying to implement an eye diagram for an application, where the input signal is QPSK. However, I feel that there is some fundamental concept concerning these plots that I am missing. Several ...
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### Why does OFDM use cyclic-prefix while QPSK uses root-raised cosine filters?

My understanding is that BPSK/QPSK/... are often implemented with root-raised cosine (RRC) filters to reduce ISI and bandwidth. OFDM can be understood to be BPSK/QPSK/... implemented on multiple ...
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### How to calculate the doppler shift?

I am writing a QPSK receiver in MATLAB. In the transmitter part, I have generated random data using randi, QPSK modulated and pulse shaped using a RRC filter. The ...